1. Field
The present disclosure is directed to a method and apparatus for dual mode power control. More particularly, the present disclosure is directed to switching between an open loop power control mode and a closed loop power control mode.
2. Description of Related Art
Presently, in Code Division Multiple Access (CDMA) systems, transmitter output power must be controlled very precisely over a wide dynamic range. Radio open loop control systems can be used to cover the wide dynamic range. Unfortunately, it is difficult to precisely control radio open loop control systems. Furthermore radio open loop control system control requires extensive pre-characterization and real time monitoring of temperature, voltage, radio frequency, and the like in order to maintain precise control of the radio power output. Radio open loop control systems are also less tolerant of power amplifier efficiency enhancement techniques, such as load switching, bias switching, and stage bypassing, because these techniques all tend to introduce power amplifier gain variations that are difficult to predict and characterize.
Precision control can be easier to maintain in a radio closed loop system. Unfortunately, radio closed loop systems do not have a wide enough dynamic range to cover CDMA operating requirements. The primary limitation of a radio closed loop system being the dynamic range of the radio frequency power detection element, which incurs significant costs and current drains when attempting to meet the CDMA dynamic range requirements.
Thus, there is a need for a radio power control system that is both precise and covers a wide dynamic range in a cost and current drain efficient manner. There is also a need for a radio power control system that can make power amplifier efficiency enhancement techniques more realizable and that can reduce the characterization and monitoring requirements of a strictly open loop control system. These and other benefits can be achieved by the teachings of the present disclosure.